Illumination optical apparatus and exposure apparatus

ABSTRACT

An illumination optical apparatus ( 14 - 40 ) and exposure apparatus ( 10 ) provided with the illumination apparatus, capable of employing a high-output light source. The illumination apparatus comprises, in order along an optical axis, a light source ( 14 ) capable of providing a primary light beam (B) having a cross-section, a condenser optical system ( 30 ) to condense the primary light beam so as to form a convergence point (F) adjacent the condenser optical system, a light-pipe optical integrator ( 160 ) having a rectangular cross-sectional shape with a first side of length dx, a second side of length dy, and a most light-source-wise incident surface ( 160   a ) axially spaced from the convergence point by a spacing (L2). The integrator is capable of forming a plurality of secondary light sources and corresponding secondary light beams (B′) from the primary light beam. Adjacent the integrator is an imaging optical system ( 40 ) to converge the primary and secondary light beams to illuminate the illumination surface. The apparatus preferably satisfies the following conditions:  
     0.1≦ L 2≦ dx /(2×tan α x )  
     0.1≦ L 2≦ dy /(2×tan α y ),  
     wherein αx is the divergence angle of the primary light beam when incident the integrator incident surface, as measured in a first plane that includes the optical axis. Likewise, αy is the corresponding angle as measured in a second plane orthogonal to the first plane. These conditions ensure that the integrator will not be damaged or otherwise broken by high concentrations of light on the integrator incident surface.  
     The exposure apparatus comprises the above-described illumination optical system and further includes a projection optical system ( 54 ) arranged adjacent the illumination surface so as to project an image of a pattern on a mask ( 48 ) onto a photosensitive substrate ( 60 ), thereby patterning the substrate.

FIELD OF THE INVENTION

[0001] The present invention relates to an illumination opticalapparatus and an exposure apparatus provided with the illuminationoptical apparatus, and more particularly relates to illumination opticalapparatus employing light pipe optical integrators.

BACKGROUND OF THE INVENTION

[0002] Japanese Patent Application Kokai No. Hei 8-6175 discloses anillumination optical apparatus suited to exposure apparatus formanufacturing semiconductor devices. This illumination optical apparatususes an internal reflection, elongate (i.e., rod-type) opticalintegrator to form a plurality of light source images from a primarylight beam from a light source. Such integrators are referred to in theart as “light pipes” and so this term is used hereinafter.

[0003] The above-mentioned prior art illumination optical apparatusincludes a condenser lens which condenses the primary light beam ontothe incident surface of the integrator. This beam is then split byinternal reflection within the light pipe into a plurality of secondarylight beams. These secondary light beams proceed in predeterminedangular directions based on the geometry of the integrator. A pluralityof light source images (i.e., virtual light sources) associated with theplurality of secondary light beams are formed along the plane of theincident surface of the integrator. The plurality of secondary lightbeams, each appearing to emanate from a corresponding light sourceimage, pass through a condenser lens and illuminate a surface to beirradiated, such as a mask.

[0004] The increasing degree of integration of semiconductor devices haslead to the commercialization and development of excimer lasers andother intense light sources for use in exposure apparatus formanufacturing semiconductor devices. Excimer lasers, for example,operate at an oscillation wavelength of 248 nm or 193 nm and have a highpower output. Accordingly, conventional illumination optical apparatus,such as that discussed immediately above, are not generally amenable foruse in an exposure apparatus employing such a high-output light source.This is because a light pipe formed of glass material is prone tobreaking due to the concentration of light energy at a convergence pointformed on the incident surface of the integrator.

SUMMARY OF THE INVENTION

[0005] The present invention relates to an illumination opticalapparatus and an exposure apparatus provided with the illuminationoptical apparatus, and more particularly relates to illumination opticalapparatus employing light pipe optical integrators.

[0006] The present invention takes the abovementioned problems intoconsideration, and has the goal of providing an illumination opticalapparatus wherein the integrator is not prone to breaking when used witha high-output light source like an excimer laser. A further goal is toprovide an exposure apparatus provided with the aforesaid illuminationoptical apparatus.

[0007] Accordingly, a first aspect of the present invention is anillumination optical apparatus for illuminating an illumination surface.The apparatus comprises, in order along an optical axis, a light sourcecapable of providing a primary light beam having a cross-section, and acondenser optical system to condense the primary light beam so as toform a convergence point adjacent the condenser optical system. Adjacentthe condenser optical system is a light-pipe optical integrator having arectangular cross-sectional shape with a first side of length dx, asecond side of length dy, and a most light-source-wise incident surfaceaxially spaced from the convergence point by a spacing L. The integratoris capable of forming a plurality of secondary light sources andcorresponding secondary light beams from the primary light beam.Adjacent the light pipe optical integrator is an imaging optical systemto converge the primary and secondary light beams to illuminate theillumination surface. The following conditions are also preferablysatisfied:

0.1≦L≦dx/(2×tan αx)

0.1≦L≦dy/(2×tan αy),

[0008] wherein αx is an angle of the primary light beam incident theincident surface, as measured in a first plane that includes the opticalaxis, and αy is an angle of the primary light beam incident the incidentsurface, as measured in a second plane orthogonal to the first plane.

[0009] A second aspect of the present invention is the optical apparatusas described above, further including first and second variable opticalmembers capable of shaping the primary light beam cross-section so as tomake this cross-section and the integrator cross-section have asubstantially similar size and shape.

[0010] A third aspect of the present invention is exposure apparatus forexposing a pattern present on a mask onto a photosensitive substrate.The exposure apparatus comprises, in order along an optical axis, theillumination optical system as described above, and a projection opticalsystem arranged adjacent the illumination surface so as to project animage of the mask arranged at the illumination surface to expose themask pattern onto the photosensitive substrate.

[0011] A fourth aspect of the invention is a method of uniformlyilluminating a surface with an illumination optical apparatus having alight pipe optical integrator with a cross-section, an incident surfaceand an exit surface. The method comprises the steps of first providing aprimary light beam having a primary light beam cross-section, thencondensing the primary light beam and forming a convergence point at aposition spaced apart from the incident surface, then collecting lightemanating from the convergence point at an angle α using the light pipeoptical integrator, then forming a plurality of secondary light sourcesand associated secondary light beams by multiply internally reflectingthe light within the light pipe optical integrator, and then finallyconverging the primary and secondary light beams emanating from the exitsurface so as to uniformly illuminate the illumination surface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1A is a schematic optical diagram in the Y-Z plane of a firstembodiment of the exposure apparatus of the present invention providedwith a first embodiment of the illumination optical apparatus of thepresent invention;

[0013]FIG. 1B is a schematic optical diagram in the X-Z plane of theexposure apparatus of FIG. 1A;

[0014]FIG. 2 is a schematic optical diagram, perspective view, of theexposure apparatus of FIG. 1A;

[0015]FIG. 3 is a schematic optical diagram, perspective view, of asection of exposure apparatus in FIG. 1 showing only a section of theillumination optical apparatus;

[0016]FIG. 4A is a schematic optical diagram in the Y-Z plane of asecond embodiment of the exposure apparatus of the present inventionprovided with a second embodiment of the illumination optical apparatusof the present invention; and

[0017]FIG. 4B is a schematic optical diagram in the X-Z plane of theexposure apparatus of FIG. 4A.

DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention relates to an illumination opticalapparatus and an exposure apparatus provided with the illuminationoptical apparatus, and more particularly relates to illumination opticalapparatus employing light pipe integrators. With reference now to FIGS.1A, 1B and FIG. 2, exposure apparatus 10 comprises, in order along anoptical axis A, a light source 14 capable of providing a primary lightbeam B having a given cross-sectional shape such as, for example,rectangular. Light source 14 may be, for example, an excimer laserproviding laser light having a wavelength of 248 nm or 193 nm. Acylindrical expander 16 is disposed at a predetermined position toreceive light beam B from the light source. Cylindrical expander 16comprises a pair of cylindrical lenses 16 a and 16 b having negativerefractive power and positive refractive power, respectively, in the X-Zplane (FIG. 1B). Lenses 16 a and 16 b function as a plane parallel platein the Y-Z plane (FIG. 1A). It is preferred that cylindrical lenses 16 aand 16 b constitute a focal zoom lens so that the rectangular ratio ofthe cross-section of light beam B can be properly modified.

[0019] A light beam shape changing system is disposed at a predeterminedposition to receive light beam B from cylindrical expander 16. The lightbeam shape changing system forms an annular light beam or a pluralitylight beams eccentric to optical axis A based on light beam B from thecylindrical expander 16. The light beam shape changing system comprisesfirst variable optical member 18 comprising a pair of conical prisms 18a and 18 b, and a second variable optical member 24 comprising a pair ofpyramidal prisms 24 a and 24 b. The construction of first and secondvariable optical members 18 and 14 are discussed in greater detailbelow. A condenser optical system 30 is disposed at a predeterminedposition to receive light beam B from the light beam shape changingsystem (18, 24). The condenser optical system 30 has a pupil plane P1and a variable focal length, and a light pipe optical integrator (i.e.,a rod-type integrator or a internal reflection-type glass rod) 36disposed at a predetermined position to receive light beam B fromcondenser optical system 30. The light pipe optical integrator includesan incident surface 36 a, an exit surface 36 b, and an outer surface36S. Integrator 36 has, in the first embodiment, a substantially squarecross-section. Integrator 36 also preferably is made of a glassmaterial, such as quartz glass or fluorite.

[0020] Adjacent integrator 36 is an imaging optical system 40 with apupil plane P2 and two lens elements 40 a and 40 b, a mask 48 withpattern (not shown) thereon, a projection optical system 54 and a wafer60 serving as a photosensitive substrate. In exposure apparatus 10,integrator exit surface 36 b and mask 48 are optically conjugate, andmask 48 and wafer 60 are optically conjugate. Elements 14-40 of exposureapparatus 10 constitute a first embodiment of the illumination opticalapparatus of the present invention.

[0021] With continuing reference to FIGS. 1A and 1B, the operation ofexposure apparatus 10 is now described. Light source 14 emits light beamB having a rectangular cross-section that extends lengthwise along theY-direction. Light beam B enters cylindrical expander 16, which expandsthe light beam in the X-Z plane (FIG. 1B and FIG. 2), so that the lightbeam has a substantially square cross-section. Light beam B exits fromcylindrical expander 16, passes through conical prisms 18 a and 18 b,and pyramidal prisms 24 a and 24 b, and enters condenser optical system30. The action of conical prisms 18 a and 18 b and pyramidal prisms 24 aand 24 b constituting first and second variable optical members 18 and24, respectively, is explained in greater detail below. It is assumed inthe explanation below that light beam B exiting cylindrical expander 16maintains its cross-sectional shape upon passing through conical prisms18 a and 18 b and pyramidal prisms 24 a and 24 b.

[0022] Light beam B passes through condenser optical system 30 andconverges at a convergence point F on optical axis A, whereupon the beamthen diverges from convergence point F at an angle α (measured withrespect to optical axis A), and then enters integrator 36. Multiplelight source images (not shown) are formed by light beam B enteringintegrator 36 through incident surface 36 a and multiply internallyreflecting from outer surfaces 36S of integrator 36. The number of lightsource images so formed corresponds to the number of internalreflections. The light source images are formed along a surface 64 thatpasses through convergence point F and that is parallel to incidentsurface 36 a of integrator 36. Accordingly, the light source images arenearly all virtual images, with only the center (i.e., convergence pointF) light source image being a real image.

[0023] Thus, the light source images (or, the multiple reflections) forma plurality of secondary light beams B′ which superimpose at exitsurface 36 b of integrator 36. Light beams B′ then pass through imagingoptical system 40, which directs the light beams to uniformly illuminatemask 48. Accordingly, a substantially square illumination field (notshown) is formed on mask 48. This illumination field is similar to thecross-sectional shape of integrator 36. Light beams B′ passing throughmask 48 then pass through projection optical system 54, which forms animage of the mask pattern on wafer 60. In this manner, the pattern ofmask 48 is successively exposed on each exposure region (not shown) ofwafer 60 by performing exposures while driving and controlling (i.e.,“stepping”) wafer 60 in the X-Y plane.

[0024] With continuing reference to FIGS. 1A and 1B, convergence point Fis spaced apart from incident surface 36 a of integrator 36 by adistance L1. In prior art apparatus, the convergence point is formed onthe incident surface of the integrator. However, in the presentinvention, such a concentration of energy on incident surface 36 aintegrator 36 is avoided. As a result, solarization is satisfactorilycontrolled, and the formation of contaminants due to photochemicalreactions is reduced. This prevents integrator 36 from being damaged orfrom breaking when used in conjunction with a high-output light sourcelike an excimer laser.

[0025] To ensure the risk of damaging or breaking integrator 36 isminimized, and to avoid optical losses at incident surface 36 a, it ispreferred that spacing L1 satisfy the following condition:

0.1 mm≦L1≦d/(2×tan α)  (1)

[0026] wherein d is the length (mm) of one side of the squarecross-sectional surface of integrator 36.

[0027] If spacing L1 falls below the lower limit in condition (1), thespacing narrows excessively, increasing the concentration of energy onincident surface 36 a. This, in turn, greatly increases the likelihoodof integrator 36 being damaged or breaking. On the other hand, ifspacing L1 exceeds the upper limit in condition (1), the spacing widensexcessively. In this case, incident light beam B no longer entirelypasses through incident surface 36 a, resulting in a loss of light (andthus exposure, energy). The optimal spacing L1 is specified within therange of condition (1) in accordance with the magnitude of the outputenergy of the light source used and the cross-sectional shape of lightbeam B.

[0028] The following is a numerical example associated with a exposureapparatus 10, representing a Working Example of the first embodiment ofthe present invention. Let L_(IN) be the axial length of integrator 36.If L_(IN)=1000 mm, the number of light source images formed (i.e., thenumber of light beams B′ into which light beam B is split due internalreflections in integrator 36) is 1024 (i.e., 32×32). If length d of oneside of the cross-section of integrator 36 is 10 mm, thenα=tan⁻¹[32×(d/2)/L_(IN)]=9.1°.

[0029] In this case, in view of condition (1), spacing L1 should be setwithin the range of 0.1 mm to 31.25 mm. To maintain a predeterminedoptical performance and to make exposure apparatus 10 compact, it ispreferable to set length L_(IN)≦1500 mm.

[0030] With reference now to FIGS. 1A, 1B and 3, the construction andaction of conical prisms 18 a and 18 b and pyramidal prisms 24 a and 24b constituting variable optical members 18 and 24, respectively, isexplained. Conical prism 18 includes a most light-source-wise incidentsurface 18 ai, which is planar and perpendicular to optical axis A.Conical prism 18 a further includes an exit surface 18 ae on the maskside (i.e., opposite incident surface 18 i) which is formed in the shapeof a conical concave surface (i.e., a frustrum) symmetric about opticalaxis A and whose concavity faces mask 48.

[0031] Conical prism 18 b includes a most light-source-wise incidentsurface 18 bi, which is formed in the shape of a conical convex surfacesymmetric about optical axis A and whose convexity faces light source14. Conical prism 18 b further includes an exit surface 18 be, oppositeincident surface 18 bi, which is planar and perpendicular to opticalaxis A.

[0032] Surface 18 ai of first conical prism 18 a and surface 18 be ofsecond conical prism 18 b are parallel to one another. Further, at leastone of first conical prism 18 a and second conical prism 18 b isconstructed so as to be moveable along optical axis A (i.e, axiallymoveable). Accordingly, there is a first state wherein surface 18 aeconformably contacts surface 18 bi. In this first state, conical prisms18 a and 18 b function as a plane parallel plate, and thecross-sectional shape of light beam B is maintained upon passing throughconical prisms 18 a and 18 b.

[0033] In contrast, in a second state, surface 18 ae is spaced apartfrom surface 18 bi. In this second state, light beam B entering conicalprisms 18 a and 18 b is shifted equidistantly outwardly along the radialdirection about optical axis A. As a result, the cross-section ofincident light beam B, which is initially square, is shaped into ahollow square cross-section 70 upon passing through spaced apart conicalprisms 18 a and 18 b (FIG. 3). Hollow square cross-section 70 includesan outer square 70 o, an inner square 70 i, and a common center Cthrough which optical axis A passes.

[0034] With continuing reference to FIGS. 1A, 1B and 3, pyramidal prism24 a includes a most light-source-wise incident surface 24 ai, which isplanar and perpendicular to optical axis A.

[0035] Pyramidal prism 24 a further includes an exit surface 24 aeopposite surface 24 ai, which is formed in the shape of a regular squarepyramidal surface (i.e., the side face of a regular square pyramid)symmetric about optical axis A and whose concavity faces mask 48.

[0036] Pyramidal prism 24 b includes a most light-source-wise incidentsurface 24 bi, which is formed in the shape of a regular squarepyramidal convex surface symmetric about optical axis A and whoseconvexity faces light source 14. Pyramidal prism 24 b further includesan exit surface 24 be, opposite surface 24 bi, which is planar andperpendicular to optical axis A.

[0037] Surface 24 ai includes four facets 84 and surface 24 bi includesfour facets 90. Facets 84 and 90 are parallel to one another. Further,at least one of first pyramidal prism 24 a and second pyramidal prism 24b is constructed so as to be moveable along optical axis A. Accordingly,in a first state, pyramidal prisms 24 a and 24 b conformably contact oneanother with contacting facets 90. In this first state, pyramidal prisms24 a and 24 b function as a plane parallel plate, and thecross-sectional shape of light beam B is maintained upon passing throughpyramidal prisms 24 a and 24 b.

[0038] On the other hand, in a second state, Pyramidal prism 24 a isspaced apart from pyramidal prism 24 b. In this second state, light beamB enters pyramidal prisms 24 a and 24 b and moves parallel from opticalaxis A toward the four corners along four radial axes (not shown) eachinclined at 45 degrees with respect to the X-axis and Y-axis. As aresult, in the second state, incident light beam B, having a squarecross-section, passes through spaced apart pyramidal prisms 24 a and 24b and is shaped into a light beam group comprising four light beams (notshown) each having a substantially square cross-section 92 (FIG. 3),with the center of each light beam substantially coincident with thefour corners of a square about optical axis A.

[0039] By setting conical prisms 18 a and 18 b and pyramidal prisms 24 aand 24 b to their respective first states, a square light source isformed in the pupil plane P1 of condenser optical system 30, andso-called normal illumination can be obtained. In addition, by settingconical prisms 18 a and 18 b to the first state or second state and alsosetting pyramidal prisms 24 a and 24 b to the second state, a quadrupolelight source (i.e., a light source comprising four light beams having asquare cross-section or hollow square cross-section) is formed in pupilplane P1 of condenser optical system 30. Thus, so-called quadrupolemodified illumination can be obtained. Furthermore, by setting conicalprisms 18 a and 18 b to the second state and also setting pyramidalprisms 24 a and 24 b to the first state, an annular light source isformed in pupil plane P1 of condenser optical system 30. Thus, so-calledannular modified illumination can be obtained.

[0040] As described above, conical prisms 18 a and 18 b and pyramidalprisms 24 a and 24 b constitute a light beam shaping apparatus forforming an annular light source in pupil plane P1 of condenser opticalsystem 30, or a plurality of light sources (four, in this case)eccentric with respect to optical axis A. By arranging conical prisms 18a and 18 b and pyramidal prisms 24 a and 24 b in exposure apparatus 10of FIG. 1 in the optical path between cylindrical expander 16 and planeP1 of condenser optical system 30, a modified light source is capable ofbeing formed in pupil plane P1. However, by arranging the same betweenintegrator 36 and the pupil plane P2 of imaging optical system 40, amodified light source is capable of being formed in pupil plane P2.

[0041] As mentioned above, the number of light source images formed insurface 64 depends upon the number of internal reflections in integrator36. Furthermore, the number of internal reflections depends upon theaxial length of integrator 36 and the numerical aperture (NA) ofincident light beam B. The NA and angle α are related by the relationNA=n×sin α, where n is the refractive index of the intervening medium,which can be taken as unity. The NA of incident light beam B changesdepending on the focal length of condenser optical system 30. Thus, bysuitably changing the focal length of condenser optical system 30, angleα (i.e., the NA) can be changed while maintaining convergence point F ata fixed position. Thus, by suitably changing the focal length ofcondenser optical system 30, the number of light source images formedcan be adjusted while reliably avoiding concentrating too much lightonto surface 36 a, and thereby avoiding the risk of breaking integrator36.

[0042] With reference now to FIG. 4, exposure apparatus 100 represents asecond embodiment of the present invention and has a constructionsimilar to that of exposure apparatus 10 of FIGS. 1A and 1B. However,whereas integrator 36 in exposure apparatus 10 has a substantiallysquare cross-section, integrator 160 of exposure apparatus 100 has asubstantially rectangular cross-section extending lengthwise along theY-direction. In the description below, elements in exposure apparatus100 having the same function as those in exposure apparatus 10 areassigned the same reference symbols. Exposure apparatus 100 is nowexplained below, with attention to the differences between exposureapparatus 10.

[0043] With continuing reference to FIG. 4 and exposure apparatus 100,light source 14 emits a substantially parallel light beam B having arectangular cross-section extending lengthwise along the Y-direction.Rectangular light beam B enters a cylindrical expander 120 comprising,for example, a pair of cylindrical lenses 16 a and 16 b (not shown inFIGS. 4A and 4B), such as those in exposure apparatus 10 (FIGS. 1A and1B). However, each cylindrical lens cylindrical expander 120respectively has negative refractive power and positive refractive powerin the Y-Z plane (FIG. 4A), and functions as a plane parallel plate inthe X-Z plane (FIG. 4B). Accordingly, light beam B entering cylindricalexpander 120 is expanded in the Y-direction, and is shaped to have arectangular cross-section extending lengthwise along the Y-direction.

[0044] Light beam B passing through cylindrical expander 120 then passesthrough conical prisms 18 a and 18 b and pyramidal prisms 24 a and 24 b,and enters condenser optical system 30. Light beam B converges atconvergence point F on optical axis A, and subsequently diverges atangle α and enters integrator 160. The latter includes an incidentsurface 160 a, an exit surface 160 b, outer surfaces 160S, and has arectangular cross-section extending lengthwise along the Y-direction. Aswith exposure apparatus 100, light beam B enters integrator 160 and,through multiple internal reflections, forms a plurality of light beamsB′. A plurality of light source images are formed in surface 64 passingthrough convergence point F and parallel to incident surface 160 a.Light beams B′, which appear to emanate from the plurality of lightsource images pass through imaging optical system 40 and uniformlyilluminate mask 48. In exposure apparatus 100, a rectangularillumination field (not shown) similar to the cross-sectional shape ofintegrator 160 is formed on mask 48. Also, elements 14-40 and 120 and160 constitute a second amendment of the illumination optical apparatusof the present invention.

[0045] With continuing reference to FIGS., 4A and 4B, convergence pointF and incident surface 160 a of integrator 160 are spaced apart by adistance L2, similar to spacing L1 of exposure apparatus 10 (FIGS. 1Aand 1B). Accordingly, unlike the prior art, a concentration of energy onincident surface 160 a is avoided. As a result, solarization issatisfactorily controlled, and the formation of contaminants due tophotochemical reactions is also reduced. This prevents integrator 160from being damaged or breaking when used in conjunction with ahigh-output light source like an excimer laser.

[0046] For integrator 160 in exposure apparatus 100, it is preferablethat adequate spacing L2 be ensured by satisfying the followingconditions (2) and (3):

0.1 mm≦L2≦dx/(2×tan αx)  (2)

0.1 mm≦L2≦<dy/(2×tan αy)  (3)

[0047] wherein dx is the length (mm) of one side of integrator 160 alongthe X-direction, and dy is the length (mm) of the other side ofintegrator 160 along the Y-direction. In addition, αx is the divergenceangle of light beam B as measured in the X-Z plane, and αy is thedivergence incident angle in light beam B as measured in the Y-Z plane.

[0048] If spacing L2 falls below the lower limit in conditions (2) and(3), the spacing is too narrow, and the likelihood of integrator beingdamaged or breaking is greatly increased.

[0049] On the other hand, if spacing L2 exceeds the upper limit inconditions (2) and (3), the spacing widens excessively, and opticallosses, i.e., (energy losses) occur at incident surface 160 a.

[0050] To maintain a predetermined optical performance and to makeexposure apparatus 100 compact, it is preferable to set the axial lengthL_(IN)≦1500 mm, i.e., the same as in exposure apparatus 10.

[0051] Also, in exposure apparatus 100, a modified light source can alsobe formed in pupil plane P2 of imaging optical system 40 by arrangingconical prisms 18 a and 18 b and pyramidal prisms 24 a and 24 b in theoptical path between integrator 160 and pupil plane P2.

[0052] As discussed above, the number of light source images formed insurface 64 depends upon the number of internal reflections in integrator36 or 160. Furthermore, the number of internal reflections depends uponthe length of the integrator and the NA (i.e., angle α) of the incidentlight beam, which can be changed by varying the focal length ofcondenser optical system 30. Accordingly, if the cross-section of theintegrator (namely, the shape of incident surface) is not similar to thecross-section of light beam B incident integrator 36 of exposureapparatus 10 or integrater 160 of exposure apparatus 100, then thenumber of light source images formed along the X-direction of surface 64will differ from the number of light source images formed along theY-direction.

[0053] Generally, in an illumination optical apparatus employing a lightpipe optical integrator, it is necessary to make the cross-section ofthe integrator and the cross-section of the light beam incident theintegrator substantially similar. This makes the number of light sourceimages formed in the orthogonal directions on the incident side of theintegrator substantially the same, which makes the resolution of theprojection optical system substantially the same in the orthogonaldirections of the exposure field. Accordingly, even in the case wherein,for example, the light beam from a mercury lamp in an exposure apparatusis converged on the incident surface of the integrator and a lightsource image is formed on the incident surface, the resolution of theprojection optical system can be made to substantially agree in theorthogonal directions of the exposure surface. This is accomplished bymaking the cross-section of the integrator and the shape of the lightsource image formed on the incident surface substantially similar inshape and size.

[0054] In the case of exposure apparatus 100, for example, if light beamB having a square cross-section is input into integrator 160 having arectangular cross-section extending lengthwise along the Y-direction,the number of light source images formed along the X-direction becomesgreater than the number of light source images formed along theY-direction. As a result, the resolution of projection optical system 54no longer coincides in the orthogonal directions (directionscorresponding to the X-axis and Y-axis) of the exposure field. Thiscreates the risk that the line width of the pattern formed on wafer 60will not be the same along orthogonal directions of the exposure field.Accordingly, to make the number of light source images formed at surface60 along the X-direction and the number of light source images formedalong the Y-direction be substantially the same, it is preferable toprovide a cylindrical expander 16 which allows for the cross-section ofintegrator 160 and the cross-section of incident beam B incident surface160 a to be substantially similar in shape and size.

[0055] In each of the exposure apparatus 10 and 100 described above,satisfactory projection and exposure can be performed under stable andsatisfactory exposure conditions without the risk of damaging orbreaking the integrator due to a high concentration of energy from ahigh-output light source, and without optical losses occurring at theintegrator's incident surface. A wafer (e.g., wafer 60) that hasundergone the exposure process (photolithography process) by exposureapparatus 10 (FIGS. 1A and 1B) or 100 (FIGS. 4A and 4B) afterwardundergoes a photoresist development process, and then an etching processthat removes undeveloped resist and etches the wafer so as to patternthe wafer, and then a resist removal process that removes the unneededresist after the etching process. Afterwards, upon completion of waferprocessing, further processes are performed in the actual assembly ofthe semiconductor device, such as dicing the wafer into its constituentprinted circuits to create chips, bonding that assigns wiring and thelike to each chip, and packaging that packages each chip.

[0056] The above explanation describes an example wherein semiconductordevices are manufactured by a photolithography process and a waferprocess employing an exposure apparatus. However, liquid crystal displaydevices, thin-film magnetic heads, and image detectors (e.g., CCDs andthe like) can also be manufactured as semiconductor devices by aphotolithography process that uses the exposure apparatus of the presentinvention.

[0057] Thus, since exposure and patterning of a wafer can be performedunder stable and satisfactory exposure conditions when manufacturingsemiconductor devices and the like using the illumination opticalapparatus of the present invention, satisfactory semiconductor devicesand the like can be manufactured with high throughput.

[0058] Each exposure apparatus of the present invention may include anillumination optical apparatus provided with a high-output light sourceother than an excimer laser light source. For example, it is alsopossible to use, as light source 14 in the present invention, a lightsource unit comprising a laser light source like an F₂ laser thatsupplies light having a wavelength of 157 nm. Alternatively, acombination of a laser light source that provides light of apredetermined wavelength and a nonlinear optical element that convertsthe light from that laser light source to light of a short wavelength of<200 nm may also be used.

[0059] In addition, each exposure apparatus of the present invention, asdiscussed above, is provided with an illumination optical apparatus ofthe present invention. However, the illumination optical apparatus canalso be applied to a general illumination optical apparatus foruniformly illuminating a surface to be irradiated other than a mask.

[0060] In the illumination optical apparatus of the present invention,as explained above, the energy acting upon the incident surface of theintegrator is significantly reduced compared with the prior art. Theillumination optical apparatus of the present invention provides lightto the integrator while avoiding an energy concentration occurring onthe incident surface of the integrator sufficient to damage or break theintegrator. Accordingly, solarization is satisfactorily controlled andthe formation of contaminants due to photochemical reactions is alsoreduced, without the risk of the integrator breaking due to the use of ahigh-output light source. This differs significantly from the prior art,wherein the convergence point is formed on the incident surface of theintegrator, creating an energy concentration sufficient to damage orbreak the integrator.

[0061] Accordingly, in an exposure apparatus of the present inventionthat incorporates the illumination optical apparatus according to thepresent invention, since there is no damage or breakage of theintegrator even if a high-output light source is used, satisfactoryprojection and exposure can be performed with high throughput understable and satisfactory exposure conditions. In addition, thesemiconductor device manufacturing method of the present inventionincludes a process that uses the illumination optical apparatus andexposure apparatus according to the present invention to pattern aphotosensitive substrate. In this manner, satisfactory semiconductordevices and the like can be manufactured, since projection and exposurecan be performed under stable and satisfactory exposure conditions.

[0062] While the present invention has been described in connection withpreferred embodiments and Working Examples, it will be understood thatit is not so limited. On the contrary, it is intended to cover allalternatives, modifications and equivalents as may be included withinthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. An illumination optical apparatus forilluminating an illumination surface, comprising, in order along anoptical axis: a) a light source capable of providing a primary lightbeam having a cross-section; b) a condenser optical system to condensesaid primary light beam so as to form a convergence point adjacent saidcondenser optical system; c) a light-pipe optical integrator having arectangular cross-sectional shape with a first side of length dx, asecond side of length dy, and a most light-source-wise incident surfaceaxially spaced from said convergence point by a spacing L, saidintegrator capable of forming a plurality of secondary light sources andcorresponding secondary light beams from said primary light beam; d) animaging optical system to converge said primary and secondary lightbeams to illuminate the illumination surface; and e) wherein thefollowing conditions are satisfied: 0.1≦L≦dx/(2×tan αx) 0.1≦L≦dy/(2×tanαy),  wherein αx is an angle of said primary light beam incident saidincident surface, as measured in a first plane that includes the opticalaxis, and αy is an angle of said primary light beam incident saidincident surface, as measured in a second plane orthogonal to said firstplane.
 2. An illumination optical apparatus according to claim 1,further including first and second variable optical members, arrangedbetween said light source and said light pipe optical integrator,capable of shaping said primary light beam cross-section so as to makesaid light beam cross-section and said light pipe optical integratorcross-sectional shape substantially similar.
 3. An illumination opticalapparatus according to claim 2, wherein said condenser optical systemhas a variable focal length to allow a change in said at least one ofangles αx and αy while maintaining said convergence point at a fixedposition.
 4. An illumination optical apparatus according to claim 1,further including first and second variable optical members capable ofshaping said light beam cross-section.
 5. An illumination opticalapparatus according to claim 4, wherein said first and second variableoptical members are capable of being arranged so as to shape said lightbeam cross-section to form an annular light source.
 6. An illuminationoptical apparatus according to claim 4, wherein said first and secondvariable optical members are capable of being arranged so as to shapesaid light beam cross-section to form a plurality of light sourceseccentric to the optical axis.
 7. An illumination optical apparatusaccording to claim 4, wherein said first variable optical membercomprises, in order along the optical axis: a) a first conical prismwith a most light-source-wise planar surface and an opposing conicalconcave surface symmetric with respect to the optical axis; b) a secondconical prism with a most light-source-wise conical convex surfacesymmetric with respect to the optical axis, and an opposing planarsurface; and c) wherein at least one of said first conical prism andsaid second conical prism is designed so as to be moveable along theoptical axis.
 8. An illumination optical apparatus according to claim 7,wherein said second variable optical member comprises, in order alongthe optical axis: a) a first pyramidal prism with a mostlight-source-wise planar surface and an opposing pyramidal concavesurface symmetric with respect to the optical axis; b) a secondpyramidal prism with a most light-source-wise pyramidal convex surfacesymmetric with respect to the optical axis, and an opposing planarsurface; and c) wherein at least one of said first pyramidal prism andsaid second pyramidal prism is designed so as to be moveable along theoptical axis.
 9. An illumination optical apparatus, comprising in orderalong an optical axis: a) a light source capable of supplying a primarylight beam having a first cross-section; b) a condenser optical systemcapable of condensing said light beam; c) a light pipe opticalintegrator having a most light-source-wise incident surface with anincident surface shape, and capable of forming, from said primary lightbeam, a plurality of secondary light sources and associated secondarylight beams; d) an imaging optical system designed to converge saidsecondary light beams to illuminate the surface to be irradiated; and e)a light beam shaping apparatus designed to shape said light beam firstcross-section to form a second light-beam cross-section having a shapesubstantially similar to said light pipe incident surface shape.
 10. Anillumination optical apparatus according to claim 9, wherein saidcondenser optical system is capable of forming a convergence pointspaced apart from said light pipe incident surface by spacing L.
 11. Anillumination optical apparatus according to claim 10, wherein saidspacing L satisfied the conditions: 0.1≦L≦dx/(2×tan αx) 0.1≦L≦dy/(2×tanαy), wherein αx is an angle in said primary light beam incident saidincident surface, as measured in a first plane that includes the opticalaxis, and αy is an angle in said incident light beam incident saidincident surface, as measured in a second plane orthogonal to said firstplane.
 12. An exposure apparatus for patterning a photosensitivesubstrate with pattern present on a mask, comprising in order along anoptical axis: a) an illumination optical system as set forth in claim 1;and b) a projection optical system arranged adjacent the illuminationsurface, with the mask arranged at the illumination surface, so as toproject the mask pattern onto the photosensitive substrate.
 13. Anexposure apparatus for exposing a pattern present on a mask onto aphotosensitive substrate, comprising in order along an optical axis: a)an illumination optical system as set forth in claim 9; and b) aprojection optical system arranged adjacent the illumination surface,with the mask arranged at the illumination surface, so as to project themask pattern onto the photosensitive substrate.
 14. A method ofuniformly illuminating a surface with an illumination optical apparatushaving a light pipe optical integrator with an integrator cross-section,an incident surface and an exit surface, comprising the steps of: a)providing a primary light beam having a primary light beamcross-section; b) condensing said primary light beam and forming aconvergence point at a position spaced apart from said incident surface;c) collecting light emanating from said convergence point at an angle αusing said light pipe optical integrator; d) forming a plurality ofsecondary light sources and associated secondary light beams by multiplyinternally reflecting said light within said light pipe opticalintegrator; and e) converging said primary and secondary light beamsemanating from said exit surface to uniformly illuminate theillumination surface.
 15. A method according to claim 14, wherein saidcondensing step b) further includes the step of varying said angle αwhile maintaining said convergence point at a fixed position.
 16. Amethod according to claim 14, further including the step after said stepa) but before said step b), of varying said primary light beamcross-section to be substantially similar in size and shape to saidintegrator cross-section.
 17. A method of patterning a photosensitivesubstrate by uniformly illuminating a mask having a pattern thereon withan exposure apparatus including a light pipe optical integrator havingan integrator cross-section, an incident surface and an exit surface,comprising the steps of: a) providing a primary light beam having aprimary light beam cross-section; b) condensing said primary light beamand forming a convergence point at a position spaced apart from saidincident surface; c) collecting light emanating from said convergencepoint at an angle α using said light pipe optical integrator; d) forminga plurality of secondary light sources and associated secondary lightbeams by multiply internally reflecting said light within said lightpipe optical integrator; e) converging said primary and secondary lightbeams emanating from said exit surface to uniformly illuminate the mask;and f) projecting an image of the mask onto the photosensitive substrateso as to form a pattern thereon.
 18. A method according to claim 17,wherein said condensing step b) further includes the step of varyingsaid angle α while maintaining said convergence point at a fixedposition.
 19. A method according to claim 17, further including the stepafter said step a) but before said step b), of varying said primarylight beam cross-section to be substantially similar in size and shapeto said integrator cross-section.